Laminate Sample #14: Prepreg Carbon / Epoxy on Aluminum Honeycomb Core
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- Опубліковано 3 бер 2020
- This sample shows how to make prepreg carbon panel with aluminum honeycomb core.
It is similar to #2 - pre-preg skins with honeycomb core. This time the core is aluminum honeycomb instead of Nomex. Aluminum core has slightly better mechanical properties and it fails in a more crushy/bendy - less crunchy way than Nomex - to use the technical terminology!
This panel is all unidirectional carbon - so on each face, all the fiber is pointing in one direction. This is stronger than a woven but much less damage-tolerant. You can see me pull a strip of uni off just by pulling the peel ply. Usually it is worth using a strip of woven material anywhere edges are cut or holes are drilled - unless you plan to laminate a secondary bonding feature or a "closeout" laminate to cap the edge of cored areas.
I didn't do anything to vent the core cells here - it is a small panel and the skins are relatively light. For heavier or thicker skins, it is a good idea to perforate the top skin so air and moisture (more of an issue with Nomex or other resin/paper honeycombs that absorb water) can escape the cells without pushing the skins off the core.
Find more about this sample at:
explorecomposites.com/materia... - Навчання та стиль
Aluminum and carbon fiber dislike each other due to dissimilar corrosion. This can become an issue later on.
Cheers on your videos keep up the good work!
Yeah - this wouldn't last long in an electrolytic situation!
@@melissahill7930 You're right - this would help - but its not very commonly done. Most carbon things made with aluminum core aren't used in a corrosive environment so its less of a big deal... and there are other cores (aramid honeycomb, foams, etc.) that solve the problem effectively. For isolating aluminum hardware - fiberglass inserts/plies/scrim are a good idea for sure.
subbed -- this is awesome content, keep it up
Thanks! I'm having fun doing it and learning a lot too!
Thank you so much! It is very useful!
We are planning to build a monocoque for a racing car using carbon fibre and aluminum honeycomb too. Is it possible to build a large and heavy weight loading structure without autoclave/oven??
I would like to share some of our projects too if you are interested. We can be contacted by email: u3534752@connect.hku.hk
Glad you found the video useful! You can build with honeycombs without prepregs but it is less ideal. For complex shapes you’ll have to cure one skin in the mold (bagged wet layup probably) then the core gets bagged in and detailed. Then you will do the inside skin using a bagged “wet preg” approach. Check out laminate sample 22 and also the wet preg one - think its around 10 or so. Also have a look at the Darkaero youtube channel.
Are there any concerns about aluminum with cf for galvination?
Oh yes, it can be an issue in plenty of situations! Often people use a glass scrim ply between the core and the carbon.
Are there any re usable type plastic films for vaccum bag?
There aren't any really good reusable options for thin films. Silicone sheet is often used but in thicker sheets or seamed or laminated custom bags that only work for one part geometry. For flat panels, silicone sheet in a "veneer press" type frame is common but expensive to set up and only really good for simple shapes.
Do you find the aluminum or armid more rigid, or does it rely more on thickness of the core ?
Stiffness will be most directly related to thickness, but density and ribbon direction matter too. Aluminum is probably more "rigid" for a given thickness and weight - but not by a whole lot.
@@ExploreComposites thank you!
Can you do a video on dry carbon and al honeycomb
There's no really ideal way to do "wet layup" of dry carbon on honeycombs because the resin wants so badly to run down and fill up the cells. Flat panels can be done like "Laminate Sample #1" - one side and then the other. For heavier reinforcements it is possible to laminate a very light skin (less than 200g/6oz) on top of the honeycomb after bonding it down to seal off the cells. Let this "scrim" cure and then add the remainder of the laminate. I'll try to do this in a future laminate sample.
@@ExploreComposites I've been curious about dry carbon on honeycomb as well. Is there not a way to bond the honeycomb to already cured sheets of fiber? This would make the most sense to me, as this would avoid resin seeping into the honeycomb. I've recently asked someone who manufacturers their own panels using dry carbon how they do their process, but I doubt I'll get an answer from them.
I'd also be curious about a honeycomb filled with a closed cell foam, it shouldn't add too much weight, but would also solve the same resin problem, or mostly as the top and bottom surfaces would have small voids in the foam, if you were to do wet layups on top of a honeycomb.
@@xaytana You can definitely bond cured sheets to honeycomb - like Laminate Sample #16: ua-cam.com/video/qL3r20hy4dM/v-deo.html
Could easily do this with cured carbon instead of G10.
Also Laminate Sample #1 uses dry carbon in a two-step process with honeycomb: ua-cam.com/video/YRpu3pb2b3U/v-deo.html
I've never used foam filled honeycomb but would love to test it out... do you know any manufacturers?
Check out Laminate Sample 22 - its Kevlar not carbon but same idea.
Another UA-camr claims you need to insert a fiberglass layer each side between the carbon fiber and aluminum to prevent galvanic corrosion.
That is a good idea if you are concerned about galvanic corrosion - which will be an issue in the presence of an electrolyte. The DarkAero project team has a great video explaining: ua-cam.com/video/yRpMZaU8zKw/v-deo.html
There are many types of projects where aluminum honeycomb is bonded to carbon without isolation - either because weight is more important than longevity or there isn't the potential for an electrolytic issue. I didn't use an isolation ply here but am planning to address the concept in a future sample. Like many composites manufacturing choices it's complicated - not a right/wrong thing.
@@ExploreComposites that’s a very well reasoned, balanced, and thorough explanation. Thank you.
If it is pre_preg why are you adding resin ?
The resin film added just to the plies facing the core is there to bond to the honeycomb. The prepreg has enough resin for itself, but not enough to bond thoroughly to core so a resin film adhesive ply is added. Debulking it to the carbon itself is a great way to make it easier to handle and more effective.
See sample #12 for what happens when you don't use prepreg film adhesive to bond core.